1. Field of the Invention
The present invention relates to a resin composition and an optical film formed by using the same, and more particularly, to a resin composition including 85 to 95 parts by weight of a matrix copolymer resin including an alkyl(meth)acrylate-based unit, an acryl-based unit containing a benzene ring, a (meth)acrylic acid unit, and 5 to 15 parts by weight of a polymer resin having a weight-average molecular weight range of 150,000 to 1,000,000 as well as an optical film formed by using the composition.
2. Description of the Related Art
Liquid crystal displays have become widespread as optical display devices, due to their lower power consumption in comparison to that of a cathode ray tube displays and ease of portability due to their small volume and lightness. In general, a liquid crystal display has a basic configuration in which polarizing plates are disposed at both sides of a liquid crystal cell, and the alignment of the liquid crystal cell may be changed according to the application of an electric field of a driving circuit. As a result, characteristics of transmitted light passing through the polarizing plates may be changed, and visualization of light may thus be realized.
In general, a polarizing plate is composed of various components and first, polarizer protective films as a protective layer are adhered to both sides of a polarizer by means of an adhesive. A drawn aligned hydrophilic polymer such as polyvinyl alcohol (PVA) with adsorbed iodine or a dichroic dye may be used as a polarizer. A polarizer protective film is used in order to increase durability and mechanical properties of the polarizer and at this time, it is important for the protective film to maintain optical properties such as polarizer polarization properties. Therefore, the polarizer protective film requires optical transparency and isotropy, while heat resistance and adhesion with respect to an adhesive/glue may act as an important factor.
A cellulose-based film such as triacetyl cellulose film, a polyester-based film, a polyacrylate-based film, a polycarbonate-based film, a cyclic olefin-based film, or a norbornene-based film may be applied to the polarizer protective film. In particular, a triacetyl cellulose-based film is most widely used.
However, since the triacetyl cellulose-based film has a small in-plane retardation value and a relatively large thickness retardation value, a retardation value may be manifested according to the application of external stress. In particular, since the triacetyl cellulose-based film has many hydrophilic functional groups, a water vapor transmission rate may be high, and as a result, polarizer polarization performance may be degraded due to the occurrence of the deformation of a protective film or the dissociation of iodine ions in the polarizer under heat resistance/humidity resistance conditions. In particular, during a high-temperature, high-humidity test of a liquid crystal display, the occurrence of the deformation of a triacetyl cellulose film may manifest non-uniform optical anisotropy in the film, and as a result, limitations such as a light-leakage phenomenon may be generated.
An acryl-based resin such as poly(meth)acrylate is also known as a material having excellent transparency and optical isotropy, but the acryl-based resin may be fragile because of low external impact resistance and polarization performance of a polarizer may be degraded under high-temperature, high-humidity conditions because of low heat and humidity resistance.